Question: Solve for $x$ and $y$ using substitution. ${2x-y = -7}$ ${y = -x-11}$
Answer: Since $y$ has already been solved for, substitute $-x-11$ for $y$ in the first equation. ${2x - }{(-x-11)}{= -7}$ Simplify and solve for $x$ $2x+x + 11 = -7$ $3x+11 = -7$ $3x+11{-11} = -7{-11}$ $3x = -18$ $\dfrac{3x}{{3}} = \dfrac{-18}{{3}}$ ${x = -6}$ Now that you know ${x = -6}$ , plug it back into $\thinspace {y = -x-11}\thinspace$ to find $y$ ${y = -}{(-6)}{ - 11}$ $y = 6 - 11$ $y = -5$ You can also plug ${x = -6}$ into $\thinspace {2x-y = -7}\thinspace$ and get the same answer for $y$ : ${2}{(-6)}{ - y = -7}$ ${y = -5}$